A type of heating and air conditioning system commonly employed is referred to as the "heat pump". In this system, a compressor cycles a refrigerant through a first evaporator-condenser and a second evaporator-condenser. A heat pump system includes the first evaporator-condenser, which is located within the building and associated with a fan system for moving air through the building, and a second evaporator-condenser located exteriorly of the building. Existing heat pump systems normally employ a fan for moving ambient air past the evaporator-condenser. In the heat mode, the first unit functions as a condenser and the second unit, located outside the building, functions as an evaporator. When the unit operates in the cooling mode, the first or indoor unit functions as a condenser, and the second, or outdoor unit, functions as an evaporator.
While this existing type of refrigerant-to-air heat pump is inherently an efficient means of heating and cooling, it has one defect in that the efficiency varies greatly according to the ambient temperature. The ambient air temperature is normally opposite of that which would produce the maximum unit efficiency. The refrigerant-to-air heat pump becomes increasingly inefficient in the heating mode as ambient temperatures drop below 40.degree. F.
Others have suggested that the heat pump system be combined with an earth coil in which the refrigerant is moved through an extended tube or conduit placed in the earth. The temperature of the earth remains much more consistent than that of the ambient air temperature. However, when attempts have been made to employ earth coils in which the refrigerant is circulated through the coil, it has been found that the amount of refrigerant coil necessary to obtain sufficient heat transfer with the earth makes the use of a refrigerant type earth coil too expensive to install to be practical. To overcome this problem, others have suggested utilizing an earth coil in which water is circulated and the water used to exchange heat with the refrigerant. However, such systems have not become commonly acceptable for a number of reasons. A primary reason is that a pipe passing through the earth does not normally afford good heat transfer. An object of this invention is to provide an improved means of achieving the transfer of heat from a water-to-earth heat exchanger. Another difficulty which has existed with previous efforts to utilize water-to-earth heat exchangers is the problem of controlling the flow of water to heat the refrigerant-to-water heat exchanger. These problems are overcome with control apparatus provided in this invention.
Others have also attempted to use water wells in system where well water is pump from the earth to a water-to-refrigerant exchanger. The problem here is that natural chemicals in well water attack the components of the exchanger and form deposits on the exchanger coils. After a length of time, the deposit build-up interferes with the heat exchange between the water and the coils. When the used water is pumped back to the earth through a second well, the possibility of aquifier contamination exists. When the water is simply wasted on the surface, aquifier depletion is a problem in most parts of the country.
Another attempt to improve the efficiency of heat pumps is the use of cooling towers. The problem with cooling towers, however, is that evaporation of water causes scaling or corrosion of tower components, and sunlight causes growth of algae. In order for cooling towers to function properly, regular and thorough preventive maintenance programs are required which are both time-consuming and expensive.
The present invention is directed towards a heat pump system for heating and air conditioning a structure employing water as a vehicle for transferring heat in a closed system which is protected from evaporation and from sunlight.
Another object of the present invention is to provide a heating and air conditioning system utilizing the heat pump principle and utilizing water as a means of transferring heat to and from the earth and in an arrangement wherein the water is maintained in a closed system substantially eliminating routine maintenance.
These general objects, as well as other and more specific objects of the invention, will be fulfilled in the following description and claims, taken in conjunction with the attached drawings.